algebra word problem

[tomdicat]

The average of four 100-point exams must be 90 or better to receive a grade A. If a student received scores of 90, 86, and 90, what minimum score does the student need on the fourth exam to earn an A?

 

[mmm4444bot]

Hi tomdicat:

We like to see some effort, on these boards. I mean, where are you stuck ?

This exercise asks you to find an unknown exam score.

As with most word problems, we begin this exercise by picking a symbol to represent the unknown exam score.

:idea: Write down your definition for any symbols you pick in math because (sometimes) you'll need to remind yourself later what the symbols mean. Plus, writing it down shows other people what you're thinking.

For example, I'll pick the symbol x, and write it down:

Let x = the fourth exam score

Now that we have a symbol to write for the unknown, we can list the four exam scores to be averaged:

86, 90, 90, x

Do you know how to calculate the average of four numbers ?

Do that with the four numbers above, and you'll have a fraction with x in the numerator. The exercise tells us that this average must be no lower than 90, so write the expression equal to 90, and you'll have an equation to solve for x -- the minimum score.

If you're still stuck, please show us what you can do, so far. Please ask specific questions, as I'm not sure what kind of help you need.

Cheers ~ Mark